Startup.cs

using System;
using System.Collections.Generic;
using System.Linq;
using System.Threading.Tasks;
using Microsoft.AspNetCore.Builder;
using Microsoft.AspNetCore.Hosting;
using Microsoft.AspNetCore.HttpsPolicy;
using Microsoft.AspNetCore.Mvc;
using Microsoft.Extensions.Configuration;
using Microsoft.Extensions.DependencyInjection;
using Microsoft.Extensions.Hosting;
using Microsoft.Extensions.Logging;
using JWTAuth.API.Data;
using Microsoft.EntityFrameworkCore;

using Microsoft.IdentityModel.Tokens;
using Microsoft.AspNetCore.Authentication.JwtBearer;
using System.Text;

namespace JWTAuth.API
{
    public class Startup
    {
        public Startup(IConfiguration configuration)
        {
            Configuration = configuration;
        }

        public IConfiguration Configuration { get; }

        // This method gets called by the runtime. Use this method to add services to the container.
        public void ConfigureServices(IServiceCollection services)
        {
            services.AddCors();
            services.AddDbContext<DataContext>(x => x.UseSqlServer(Configuration.GetConnectionString("DefaultConnection")));
            services.AddControllers()
                .AddNewtonsoftJson();
            services.AddScoped<IAuthRepository, AuthRepository>();

            var key = Encoding.ASCII.GetBytes(Configuration.GetSection("AppSettings:Token").Value);
            
            services.AddAuthentication(JwtBearerDefaults.AuthenticationScheme)
            .AddJwtBearer(options => {
                options.TokenValidationParameters = new TokenValidationParameters{
                    ValidateIssuerSigningKey = true,
                    IssuerSigningKey = new SymmetricSecurityKey(key),
                    ValidateIssuer = false,
                    ValidateAudience = false
                };
            });
        }

        // This method gets called by the runtime. Use this method to configure the HTTP request pipeline.
        public void Configure(IApplicationBuilder app, IWebHostEnvironment env)
        {
            if (env.IsDevelopment())
            {
                app.UseDeveloperExceptionPage();
            }
            else
            {
                // The default HSTS value is 30 days. You may want to change this for production scenarios, see https://aka.ms/aspnetcore-hsts.
                app.UseHsts();
            }
            app.UseCors(x => x.AllowAnyHeader().AllowAnyMethod().AllowCredentials());
            app.UseHttpsRedirection();

            app.UseRouting();
            app.UseAuthentication();
            app.UseAuthorization();
            
            app.UseEndpoints(endpoints =>
            {
                endpoints.MapControllers();
            });
        }
    }
}